A wide variety of medical devices have been developed in order to deliver stimulation therapy to the patient. An implantable pulse generator (IPG) system generally refers to a medical device that delivers pulses of therapeutic stimulation to a patient. IPG systems include an IPG device and one or more implantable medical leads coupled to the IPG device. The IPG device comprises a housing that houses circuitry for the generation of therapeutic stimulation pulses, and the leads position electrodes within the patient at locations desirable for delivery of the stimulation pulses. The IPG device is typically a biocompatible hermetically sealed structure that, like the leads, is implanted in the patient. However, in some cases, only the leads are implanted, and the IPG device resides at a location external to the patient.
One common example of an IPG device is a pacemaker. A pacemaker system typically includes a pacemaker device and one or more pacing and sensing leads for delivery of pacing pulses to a patient's heart. Another example of an IPG device is a combination pacemaker-cardioverter-defibrillator. Other examples include implantable brain stimulators, implantable gastric system stimulators, implantable nerve stimulators or muscle, stimulators, implantable lower colon stimulators, and so on.
Tri-phasic pulse generation refers to a pulse generation technique that uses three phases in a pulse generation cycle. In particular, tri-phasic pulse generation involves a pre-stimulus phase, a stimulus phase, and a post-stimulus phase. During the pre-stimulus and post-stimulus phases an output capacitor is charged, whereas during the stimulus phase the output capacitor is discharged to deliver the stored charge to the patient as a stimulation pulse. More specifically, during the pre-stimulus phase, the output capacitor is charged to a desired voltage level for stimulation, during the stimulus phase, the capacitor is discharged, and during the post-stimulus phase recharging of the capacitor begins anew.